Chand N, Kumar K, Suthar S. Enhanced wastewater nutrients removal in vertical subsurface flow constructed wetland: Effect of biochar addition and tidal flow operation.
Chemosphere 2022;
286:131742. [PMID:
34352544 DOI:
10.1016/j.chemosphere.2021.131742]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 07/25/2021] [Accepted: 07/29/2021] [Indexed: 06/13/2023]
Abstract
Dissolved oxygen (DO) and carbon stock in substrate medium play a vital role in the nutrient removal mechanism in a constructed wetland (CW). This study compiles the results of dynamics of DO, ammonium N (NH4+-N), nitrate (NO3-N), sulfate (SO4-2), phosphate (PO4-3), chemical oxygen demand (COD), in three setups of vertical-flow constructed wetlands (TFCWs) (SB: substrate + biochar; SBP: substrate + biochar + Colocasia esculenta plantation; SP: substrate + Colocasia esculenta (SP), operated with tidal flow cycles. Experimental analyses illustrated the continuous high DO level (2.743-5.66 mg L-1) in SB and SBP after the I and II cycle of tidal flow (72 h flooding and 24 h dry phase). COD reduction efficiencies increased from 15.75 - 61.86% to 48.55-96.80% after tidal operation among operating TFCWs. N (NH4+-N) and N (NO3-N) removal were found to be 88.16%, and 76.02%; 49.32, and 57.85%; and 40.23%, and 48.94 % in SBP, SP and SB, respectively. The theory of improved nitrification and adsorption through biochar amended substratum was proposed for TFCW systems. PO4-3 and SO4-2 removal improved from 22.63 to 80.50%, and 19.69 to 75.20%, respectively after first tidal operation in all TFCWs. The microbial inhabitation on porous biochar could promote the transformation of available P into microbial biomass and also helped by the plant uptake process while SO4-2 reduction in TFCWs could be mainly due to sulfate-reducing bacterial activity and nitrate reduction process, mainly facilitated by high DO and biochar addition in such setups. The study suggests that effluent re-circulation through tidal operation and biochar supplementation in the substratum could be an effective mechanism for the improvement of the working efficiencies of CWs operated with low energy input systems.
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